Correlation effects on the electronic structure of 1 × 1 and 2 × 1 reconstructed Si(111) surfaces

Intra-atomic correlations are shown to lead to two separate occupied dangling-bond bands at the buckled Si(111) surface, in agreement with recent photoemission results. A bandwidth of 0.4 eV and spin-polarized bands are obtained when the atomic and spin periodicities are both 2 ×{} 1. The bandwidths are sensitive to the type of spin ordering at the surface. Nearly dispersionless bands result when the atomic and spin periodicities are 2 ×{} 1 and 1 ×{} 2, respectively. For the nonbuckled surface a metastable, antiferromagnetic structure with a 1.1-eV gap is predicted.